In an LTE (Long Term Evolution) mobile communication system, when determining that a radio quality in a specific frequency cell satisfies a reselection criterion, a mobile station UE in an Idle state activates a timer Treselection configured to measure a period during which the radio quality in the specific frequency cell continues to satisfy the reselection criterion.
Thereafter, when the timer Treselection expires, the mobile station UE in the Idle state reselects the specific frequency cell as a cell for the mobile station UE to newly stand by.
In contrast, when detecting that the radio quality in the specific frequency cell does not satisfy the reselection criterion any more, the mobile station UE in the Idle state resets the timer Treselection.
Meanwhile, in the LTE mobile communication system, when determining that a radio quality in a specific frequency cell satisfies a reporting criterion, a mobile station UE in an RRC_Connected state activates a timer Ttrigger configured to measure a period during which the radio quality in the specific frequency cell continues to satisfy the reporting criterion.
Thereafter, when the timer Ttrigger expires, the mobile station UE in the RRC_Connected state transmits a “Measurement Report” including the radio quality in the specific frequency cell to a radio base station eNB.
In contrast, when detecting that the radio quality in the specific frequency cell does not satisfy the reporting criterion any more, the mobile station UE in the RRC_Connected state resets the timer trigger.
Meanwhile, in the LTE mobile communication system, when the mobile station UE in the Idle state can standby in multiple different frequency cells, the radio base station eNB can assign a priority for each frequency cell for the mobile station UE in the Idle state, the priority being used in cell reselection.
However, the conventional LTE mobile communication system has the following problem. Specifically, when the timer Treselection is activated for multiple frequency cells assigned different priorities, it is not clear how the mobile station UE should perform the cell reselection.
In the conventional LTE mobile communication system, it is not specified that the radio base station eNB can assign priorities to be used in transmitting a “Measurement Report.” If the specification is provided, it is assumed that the same problem as the problem in the aforementioned cell reselection occurs.